Positron emission tomography with 11C-methionine and computed tomography of intracranial tumours compared with histopathologic examination of multiple biopsies

A selected group of 36 patients with suspected supratentorial gliomas were investigated with positron emission tomography (PET) using 11C-methionine and transmission computed tomography (CT) before and after intravenous injection of contrast medium. Every examination was performed with the head fixed in a plastic helmet and a baseplate to guarantee that the slice orientation was the same at examinations with the two modalities and over time. Guided by the examinations, multiple stereotactic biopsies were performed with the biopsy instrument mounted on the baseplate. Regional accumulation of methionine was compared with histology of the corresponding samples and with attenuation before and after injection of contrast medium as well as mass effect on CT. Typically, there was a low attenuating lesion with a slight mass effect on CT. There was an increased accumulation compared with normal brain tissue in 31 cases of tumours and ordinary or decreased accumulation in 3 cases of tumours. In 22 cases with increased accumulation of methionine the extension of the tumour judged by PET corresponded with that of histology. In 4 cases tumour cells were found outside the area with pathologic methionine uptake. In 5 patients there were areas with increased methionine accumulation where no tumour cells were found. In 22 cases PET using methionine was more accurate than CT in defining the tumour boundaries as determined from the histologic findings. Four groups of biopsy specimens with different amounts of methionine accumulation are described. The uptake in a single biopsy gives good but not exact information about the histology of the specimen.     

Usefulness of <Superscript>11</Superscript>C-methionine PET in the evaluation of brain lesions that are hypo- or isometabolic on <Superscript>18</Superscript>F-FDG PET

The fact that some brain tumors show hypo- or isometabolism on fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) has caused problems in the detection of primary or recurrent tumors and in the differentiation from benign lesions. We investigated the usefulness of carbon-11 methionine PET in characterizing brain lesions under these conditions. 11C-methionine PET was performed in 45 patients with brain lesions (in 34 for initial diagnosis and in 11 for detection of recurrence) that showed hypo- or isometabolism compared with normal brain tissue on FDG PET. Ten minutes after the injection of 555-740 MBq of 11C-methionine, attenuation-corrected brain images were obtained with a dedicated PET scanner. The brain lesions comprised 24 gliomas, five metastatic brain tumors, four meningiomas, two other brain tumors and ten benign lesions (including three cases of cysticercosis, two cases of radiation necrosis, one tuberculous granuloma, one hemangioma, one benign cyst, and one organizing infarction). Proliferative activity was measured using the Ki-67 immunostaining method in glioma tissues. Thirty-one of 35 brain tumors (89% sensitivity) showed increased 11C-methionine uptake despite iso- or hypometabolism on FDG PET. By contrast, all ten benign lesions showed decreased or normal 11C-methionine uptake (100% specificity). Twenty-two of 24 gliomas (92%) showed increased 11C-methionine uptake, the extent and degree of which exceeded 18F-FDG uptake, and the 11C-methionine uptake correlated with the proliferation index (r=0.67). The mean (+/-SD) uptake ratios of glioma to normal brain on FDG and 11C-methionine PET were 0.92+/-0.34 and 2.54+/-1.25, respectively. All metastatic tumors except one showed intense 11C-methionine uptake in the entire tumor or in the peripheral margin of the tumor. In meningiomas, 11C-methionine uptake showed a variable increase. In conclusion, brain lesions that show hypo- or isometabolism on FDG PET can be detected and differentiated with high sensitivity and good contrast using 11C-methionine PET. 11C-methionine PET can provide additional information when used in combination with FDG PET in the evaluation of these patients.     

Combined 18F-FDG and 11C-methionine PET scans in patients with newly progressive metastatic prostate cancer.

Metastatic prostate cancer may respond initially to hormone suppression, with involution of tumor sites, but ultimate tumor progression is inevitable. Our aim was to detect the proportion of bone and soft-tissue lesions that represent metabolically active tumor sites in patients with progressive metastatic prostate cancer. METHODS: In a prospective study, we compared 18F-FDG and L-methyl-11C-methionine (11C-methionine) PET with conventional imaging modalities (CIM), which included the combination of 99mTc-methylene diphosphonate scintigraphy, CT, or MRI. Twelve patients with prostate cancer, increasing levels of prostate-specific antigen (PSA), and at least 1 site (index lesion) with new or increasing disease on CIM were studied. The total numbers of soft-tissue and bone-tissue lesions, in a site-by-site comparison, were calculated for all imaging modalities. RESULTS: The sensitivities of 18F-FDG PET and 11C-methionine PET were 48% (167/348 lesions) and 72.1% (251/348 lesions), respectively, with CIM being used as the 100% reference (348/348). 11C-Methionine PET identified significantly more lesions than 18F-FDG PET (P < 0.01). All 12 patients with progressive metastatic prostate cancer had at least 1 lesion site of active metabolism for 18F-FDG or 11C-methionine, which could be used as an index lesion to monitor the metabolic response to therapy. A significant proportion of lesions (26%) had no detectable metabolism of 18F-FDG or 11C-methionine. Although technical factors cannot be totally excluded, we believe that metabolically inactive sites may be necrotic or dormant. More than 95% (251/258) of metabolically active sites (72% of the total number of lesions detected by CIM) metabolize 11C-methionine. 18F-FDG uptake is more variable, with 65% of metabolically active sites (48% of the total number of lesions detected by CIM). CONCLUSION: These findings reflect the different biologic characteristics of the lesions in a heterogeneous tumor such as prostate cancer and suggest that a time-dependent metabolic cascade may occur in advanced prostate cancer, with initial uptake of 11C-methionine in dormant sites followed by increased uptake of 18F-FDG during progression of disease.     

Cavernous haemangioma in the cavernous sinus: case report and review of the literature

We report a cavernous haemangioma in the left cavernous sinus. This lesions very rarely occurs in this site and is difficult to diagnose correctly preoperatively. CT, angiography and MRI permit differentiation of the cavernous haemangioma from other tumours in this region and thereby contribute to a better surgical approach. The radiological features of cavernous haemangioma reported in the literature are summarised. Received: 24 February 1999 Accepted: 1 September 2000     

PET/CT and MRI of intra-osseous haemangioma of the tibia

Intra-osseous haemangioma is a rare, benign neoplasm that usually involves the vertebrae and craniofacial bones. Furthermore, its occurrence in the long bones is extremely rare. We report the findings of fluorine-18-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT and MRI in a patient with intra-osseous haemangioma in the proximal tibia, who was initially misdiagnosed as having a malignancy based on (18)F-FDG PET/CT. (18)F-FDG PET/CT showed a well-marginated osteolytic lesion with abnormal FDG uptake. The mass demonstrated low signal intensity on T(1) weighted MRI. On T(2) weighted images, the lesion appeared as a cluster of high signal intensity lobules and showed strong enhancement on contrast-enhanced T(1) weighted images. Surgical curettage was performed and histopathological examination of the excised tissue confirmed a cavernous haemangioma.     

11C-methionine PET/CT in 99mTc-sestamibi-negative hyperparathyroidism in patients with renal failure on chronic haemodialysis

Purpose Scintigraphic localisation of parathyroid glands is often unsuccessful in patients with renal failure on chronic haemodialysis who have secondary hyperparathyroidism (HPT). The purpose of this study was to investigate the use of ¹¹C-methionine PET/CT to detect hyperfunctioning parathyroid glands in patients with renal failure on chronic haemodialysis who had ^99mTc-sestamibi-negative HPT. Methods ¹¹C-methionine PET/CT was performed in 18 patients (11 women and 7 men, aged 42–79 years; mean age 57.8 years) on haemodialysis for renal failure (2–14 years’ duration), with normo-, hypo- or hypercalcaemia and HPT not localised by either dual-tracer ^99mTc-pertechnetate/^99mTc-sestamibi subtraction scans or dual-phase ^99mTc-sestamibi scans. Results In three of ten patients with normo- or hypocalcaemic HPT there was increased ¹¹C-methionine accumulation in one gland. Seven of eight patients with hypercalcaemic HPT showed increased uptake: in five of these patients increased ¹¹C-methionine accumulation was present in one gland, while in two it was demonstrated in two glands. All patients also had high-resolution ultrasound of the neck and were treated with subtotal parathyroidectomy, leaving a remnant of the smallest of the four glands. Regardless of their size, all glands with abnormal ¹¹C-methionine parathyroid uptake were removed, and all demonstrated parathyroid hyperplasia. All patients developed post-parathyroidectomy hypoparathyroidism and one patient with normocalcaemic HPT relapsed 8 months after surgery. Conclusion These data suggest that ¹¹C-methionine PET/CT may be used to identify hyperfunctioning parathyroid glands in non-primary HPT, and especially hypercalcaemic HPT, when conventional ^99mTc-sestamibi imaging is non-localising.     

Quantitative volumetric analysis of gliomas with sequential MRI and 11C-methionine PET assessment: patterns of integration in therapy planning

Purpose

The aim of the study was to evaluate the volumetric integration patterns of standard MRI and ¹¹C-methionine positron emission tomography (PET) images in the surgery planning of gliomas and their relationship to the histological grade.

Methods

We studied 23 patients with suspected or previously treated glioma who underwent preoperative ¹¹C-methionine PET because MRI was imprecise in defining the surgical target contour. Images were transferred to the treatment planning system, coregistered and fused (BrainLAB). Tumour delineation was performed by ¹¹C-methionine PET thresholding (vPET) and manual segmentation over MRI (vMRI). A 3-D volumetric study was conducted to evaluate the contribution of each modality to tumour target volume. All cases were surgically treated and histological classification was performed according to WHO grades. Additionally, several biopsy samples were taken according to the results derived either from PET or from MRI and analysed separately.

Results

Fifteen patients had high-grade tumours [ten glioblastoma multiforme (GBM) and five anaplastic), whereas eight patients had low-grade tumours. Biopsies from areas with high ¹¹C-methionine uptake without correspondence in MRI showed tumour proliferation, including infiltrative zones, distinguishing them from dysplasia and radionecrosis. Two main PET/MRI integration patterns emerged after analysis of volumetric data: pattern vMRI-in-vPET (11/23) and pattern vPET-in-vMRI (9/23). Besides, a possible third pattern with differences in both directions (vMRI-diff-vPET) could also be observed (3/23). There was a statistically significant association between the tumour classification and integration patterns described above (p?Conclusion The metabolically active tumour volume observed in ¹¹C-methionine PET differs from the volume of MRI by showing areas of infiltrative tumour and distinguishing from non-tumour lesions. Differences in ¹¹C-methionine PET/MRI integration patterns can be assigned to tumour grades according to the WHO classification. This finding may improve tumour delineation and therapy planning for gliomas.     

Clinical positron emission tomography for brain tumors: comparison of fludeoxyglucose F 18 and L-methyl-11C-methionine.

PURPOSETo evaluate the differences between fludeoxyglucose F 18 (FDG) and L-methyl-11C-methionine (11C-methionine) as tracers for positron emission tomography (PET) in the evaluation of brain tumors.METHODSWe analyzed 10 patients with histologically verified cerebral glioma or meningioma and 1 patient with a neuroradiologic diagnosis of low-grade glioma by using FDG, 11C-methionine, and PET. We qualitatively and quantitatively evaluated the extent and degree of accumulation of FDG and 11C-methionine in the tumor tissue.RESULTSAlthough PET with FDG depicted malignant tumors as a hot spot in all cases, it was not able to delineate the extent of the tumor. Conversely, PET with 11C-methionine outlined the tumors as areas of increased accumulation of 11C-methionine, regardless of the degree of malignancy.CONCLUSIONPET with FDG and with 11C-methionine can play complementary roles in the evaluation of brain tumors.     

Comparison of 11C-methionine PET and 18F-fluorodeoxyglucose PET in differentiated thyroid cancer

BACKGROUND: The purpose of this prospective study is to evaluate the possibility of 11C-methionine (Met) PET compared with 18F-fluorodeoxyglucose (FDG) PET for the detection of recurrent or metastatic disease in patients with differentiated thyroid cancer (DTC). MATERIALS AND METHODS: Twenty patients with clinical suspicion of recurrent DTC but negative posttreatment 131I-whole body scans were included in the study. Both 11C-Met PET and 18F-FDG PET were performed within 1 week. PET images were analyzed by two independent and blinded physicians using visual and standardized uptake value analysis. PET results were also correlated with radiologic and/or cytological investigations. RESULTS: Thirteen patients showed concordant findings on both PET scans: six patients showed uptake and in seven no uptake was observed. In six of the seven patients without Met and FDG uptake, additional MRI and ultrasound-guided fine needle aspiration cytology of the lymph nodes revealed inconclusive or negative results. Six patients showed discordant findings on the PET scans: in three patients uptake was only observed on the Met PET, confirmed by MRI in one. In three patients lesions were seen on the FDG PET, confirmed by computed tomography or ultrasound-guided fine needle aspiration cytology. However, those lesions were not compatible with the lesions seen on the Met PET. In general, FDG uptake appeared to be higher than Met uptake, but was not significant (P=0.075). CONCLUSION: This study shows that imaging using radiolabeled amino acids is feasible in DTC. For now, 11C-Met PET has not proven to be superior to 18F-FDG PET in the detection of recurrent disease in DTC. Complementary uptake of Met and FDG has, however, been observed, which has to be further clarified and long-term follow-up is needed to define the true clinical value of the 11C-Met PET, and possible other amino acids tracers.     

PET/CT with intravenous contrast can be used for PET attenuation correction in cancer patients

Purpose If the CT scan of a combined PET/CT study is performed as a full diagnostic quality CT scan including intravenous (IV) contrast agent, the quality of the joint PET/CT procedure is improved and a separate diagnostic CT scan can be avoided. CT with IV contrast can be used for PET attenuation correction, but this may result in a bias in the attenuation factors. The clinical significance of this bias has not been established. Our aim was to perform a prospective clinical study where each patient had CT performed with and without IV contrast agent to establish whether PET/CT with IV contrast can be used for PET attenuation without reducing the clinical value of the PET scan.Methods A uniform phantom study was used to document that the PET acquisition itself is not significantly influenced by the presence of IV contrast medium. Then, 19 patients referred to PET/CT with IV contrast underwent CT scans without, and then with contrast agent, followed by an ¹⁸F-fluorodeoxyglucose whole-body PET scan. The CT examinations were performed with identical parameters on a GE Discovery LS scanner. The PET data were reconstructed with attenuation correction based on the two CT data sets. A global comparison of standard uptake value (SUV) was performed, and SUVs in tumour, in non-tumour tissue and in the subclavian vein were calculated. Clinical evaluation of the number and location of lesions on all PET/CT scans was performed twice, blinded and in a different random order, by two independent nuclear medicine specialists.Results In all patients, the measured global SUV of PET images based on CT with IV contrast agent was higher than the global activity using non-contrast correction. The overall increase in the mean SUV (for two different conversion tables tested) was 4.5±2.3% and 1.6±0.5%, respectively. In 11/19 patients, focal uptake was identified corresponding to malignant tumours. Eight out of 11 tumours showed an increased SUV_max (2.9±3.1%) on the PET images reconstructed using IV contrast. The clinical evaluation performed by the two specialists comparing contrast and non-contrast CT attenuated PET images showed weighted kappa values of 0.92 (doctor A) and 0.82 (doctor B). No contrast-introduced artefacts were found.Conclusion This study demonstrates that CT scans with IV contrast agent can be used for attenuation correction of the PET data in combined modality PET/CT scanning, without changing the clinical diagnostic interpretation.     

Schwannoma of the extremities: the role of PET in preoperative planning.

The aim of this study was to determine the relative utility of various preoperative diagnostic imaging modalities for the evaluation of benign schwannoma, including positron emission tomography (PET) utilising fluorine-18 fluoro-2-deoxy-D-glucose (FDG) and fluorine- 18 alpha-methyl tyrosine (FMT). computed tomography (CT), magnetic resonance imaging (MRI) and digital subtraction angiography (DSA). We retrospectively reviewed imaging findings in 22 patients with 25 histopathologically documented benign schwannomas of the extremities. Pre-operative imaging included: FDG-PET (n=22), FMT-PET (n=17), MRI (n=25), CT (n=16) and DSA (n=17). All 22 lesions examined by PET with FDG and/or FMT showed accumulation. The standardised uptake values (SUVs) for FDG-PET for the 22 examined tumours ranged from 0.33 to 3.7, and eight of them (36.4%) were assessed as malignant on the basis of their uptake. The SUVs for FMT ranged from 0.44 to 1.47, and 15 out of the 17 evaluated (88.2%) showed values indicating the tumour to be benign. CT demonstrated variable attenuation and contrast enhancement. MRI signal characteristics were relatively consistent: iso-signal or darker than skeletal muscle on T1-weighted and isosignal or brighter than subcutaneous fat on T2-weighted images. The venous tumour staining depicted on DSA was found to be significantly correlated with FDG accumulation. All tumours but one were treated by surgical enucleation. One tumour suspected to be malignant on the basis of imaging findings was treated with primary wide resection. Although CT, MRI and PET studies are all useful for the detection and localisation of schwannoma, our findings suggest that, among the imaging modalities studied, FMT-PET may be the most reliable technique for the differentiation of benign schwannoma from malignancy.     

Application of a kinetic model on the methionine accumulation in intracranial tumours studied with positron emission tomography

Eleven patients were studied with positron emission tomography (PET) using 11C-methionine. They all had low-grade astrocytomas (Kernohan grade II). The PET studies were analyzed with a metabolic model to obtain values for the influx, the accumulation rate and the partition coefficient of methionine in normal and tumourous tissue. Seven of the tumours showed an increased accumulation of methionine as compared with normal tissue on the static PET scans and also had higher values as to the kinetic parameters. Four tumours had a methionine accumulation equal to or lower than that of normal tissue and the kinetic parameters were also lower. Application of the kinetic model did not aid significantly in the delineation of the tumours. There was a correlation between the three parameters indicating an adaptation of the transport of methionine to the regional metabolic demand. The accumulation rate for normal cortical tissue was 0.49 nmol/g/min, the influx 0.97 nmol/ml and the partition coefficient 0.45 ml/g. These values are considerably higher than those previously reported. The differences might be attributed to differences in the corrections introduced for i.a. the occurrence of labelled metabolites in serum. With the use of a kinetic model, more information about the tracer is utilized and gained compared with the previously used graphic approach.     

Positron emission tomography and computed tomography in differential diagnosis between recurrent or residual glioma and treatment-induced brain lesions

In previous studies of supratentorial gliomas with positron emission tomography (PET) and computed tomography (CT), high uptakes of L-methyl-11C-methionine (11C-L-methionine) were found even in astrocytomas without blood-brain barrier defects as judged by CT or 68Ga-EDTA PET. In a number of patients examined after radiation therapy, there were no consistent changes in the high uptake values. In the present investigation PET and CT were compared with regard to their abilities to visualize and delineate recurrent tumors and treatment-induced brain defects and to differentiate between them. The study was undertaken on four patients who were long-term survivors after treatment for high-grade gliomas. For PET, 11C-L-methionine and 68Ga-EDTA were used. In two patients recurrent/residual tumors appeared considerably larger with 11C-L-methionine PET than with CT or 68Ga-EDTA PET. In one patient, no signs of recurrence were seen with any of these three methods, and in a fourth patient, whose condition was clinically stable, the findings at PET with 11C-L-methionine were non-specific. In areas corresponding to the surgical parenchymal defects, the 11C-L-methionine uptake and, except in one case, the local blood volume was markedly reduced. PET with 11C-L-methionine thus has a potential for distinguishing between postoperative brain lesions and tumor recurrence with a higher accuracy than CT.     

Contribution of PET in the detection of liver metastases from pancreatic tumours

AIM: Although uptake of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) in the liver is basically high, metastatic liver tumours are known to be positive on positron emission tomography (PET). The purpose of this study is to evaluate the diagnostic accuracy of FDG-PET in detecting hepatic metastases from pancreatic cancer. METHODS: Thirty-four patients with histologically proven malignant tumours of the pancreas underwent FDG-PET, computed tomography (CT) and transabdominal ultrasound (US). The findings of PET, CT and US were compared with the histopathologic findings at surgery or with clinical follow-up and the diagnostic accuracy of PET was evaluated. RESULTS: PET showed 28 regions of high FDG uptake (SUV = 3.3-9.1) in 13 patients. Twenty-six foci were metastatic lesions confirmed by surgery (n = 11), clinical follow-up (n = 10) or autopsy (n = 5). FDG-PET accurately differentiated seven metastatic lesions from cysts when the diagnosis by US or CT was unreliable because of the small size of the lesion. In two patients who had areas of high uptake in the liver, no metastases were detected by surgery. FDG-PET showed no areas of increased uptake in 21 patients. Surgery revealed no metastatic lesions in the liver in 20 of 21 patients, but a liver metastasis was found at surgery in one patient. The diagnostic accuracy of FDG-PET was 90%, which was comparable with that of US or CT. CONCLUSION: Our data suggest that PET is reliable in detecting liver, metastases from pancreatic cancer.     

Multiple Myeloma: Molecular Imaging with 11C-Methionine PET/CT--Initial Experience

PURPOSE: To prospectively assess molecular imaging of multiple myeloma (MM) by using the radiolabeled amino acid carbon 11 ((11)C) methionine and positron emission tomography (PET)/computed tomography (CT). MATERIALS AND METHODS: The study was approved by the institutional local ethics committee and the national radiation protection authorities. All patients with MM and control patients gave written informed consent. Nineteen patients with MM (11 women, eight men; age range, 42-64 years) and 10 control patients with hyperparathyroidism without hematologic diseases (six women, four men; age range, 43-75 years) underwent PET/CT 20 minutes after injection of a mean of 1.0 GBq +/- 0.2 (standard deviation) (11)C-methionine. Presence and extent of CT-assessed tumor manifestations and (11)C-methionine bone marrow (BM) uptake were determined on the basis of maximum standardized uptake value (SUV(max)). BM imaging patterns, normal BM, and maximal lesion (11)C-methionine uptake in patients with MM were compared with those in control patients. In two patients with MM, sulfur 35 ((35)S) methionine uptake in freshly isolated BM plasma cells was measured. Values for SUV(max) of groups were compared by using the Mann-Whitney test on a per-patient basis. RESULTS: (35)S-methionine uptake of plasma cells was five- to sixfold higher than in normal BM cells. (11)C-methionine BM uptake in control patients was homogeneous and low. All patients with MM except one with exclusively extramedullary myeloma had (11)C-methionine-positive lesions. Maximal lesion and normal BM (11)C-methionine mean SUV(max) were 10.2 +/- 3.5 and 4.3 +/- 2.0, respectively, and thus were significantly higher than that of BM in the control group (mean, 1.8 +/- 0.3; P < .001). Extramedullary MM was clearly visible in three patients (mean SUV(max), 7.2 +/- 2.4). Additional (11)C-methionine-positive lesions in normal cancellous bone were found in nearly all patients with MM. In pretreated patients with MM, a moderate fraction of osteolytic lesions had no (11)C-methionine uptake. CONCLUSION: On the basis of increased methionine uptake in plasma cells, active MM can be imaged with (11)C-methionine PET/CT.     

<Superscript>11</Superscript>C-metomidate PET imaging of adrenocortical cancer

The diagnostic potential of positron emission tomography (PET) with carbon-11 metomidate in patients with adrenocortical cancer (ACC) was evaluated. Thirteen PET examinations were performed in 11 patients with CT-detected primary tumours or recurrence and/or metastases from a previously histopathologically proven ACC. The findings at PET were compared with those at CT and verified by histopathology. Six studies (group A) were performed in patients who at the time of imaging were free of medication that could interfere with 11beta-hydroxylase activity and thereby tracer uptake at PET, such as adrenal steroid inhibitors or chemotherapy. The remaining seven studies (group B) were carried out in patients who were monitored during treatment with one or a combination of these drugs. PET visualised all viable tumours with high tracer uptake, and revealed two more lesions than were seen on CT. Three necrotic tumours were detected as false negative observations, as confirmed at surgery and histopathological examination. A true negative observation was obtained at PET in the case of a suspected liver metastasis on CT that was found to have fat vacuolation at histopathological examination of an ultrasonically guided core biopsy specimen. Group A showed apparently higher uptake in normal tissues than group B (adrenal, P=0.03; liver, P=0.01). The metomidate uptake was increased in tumour lesions as compared with normal tissues (adrenal, P=0.02; liver, P=0.005). ACC could be clearly visualised with (11)C-metomidate PET except when the tumour was necrotic. Medication with adrenal steroid inhibitors and chemotherapy decreased the tracer uptake.     

18F-FDG PET/CT Diagnosis of Vagus Nerve Neurolymphomatosis

ABSTRACT: A 62-year-old woman was in remission from previously treated stage IV diffuse large B-cell lymphoma with cranial involvement. She presented with new-onset hoarseness of voice and choking; MRI of the brain showed disease recurrence in the left cavernous sinus. She was subsequently referred for F-FDG PET/CT with contrast for further evaluation of lymphomatous recurrence. F-FDG PET/CT not only revealed hypermetabolic activity in the left cavernous sinus correlating to the MRI findings but also showed an interesting manifestation explaining the patient's hoarseness of voice, being neurolymphomatosis along the left vagus nerve.     

Positron emission tomography compared with magnetic resonance imaging and computed tomography in supratentorial gliomas using multiple stereotactic biopsies as reference

Ten patients with findings at computed tomography (CT) suggesting intracranial supratentorial glioma were investigated to compare the diagnostic efficacy of this technique with that of positron emission tomography (PET) using 11C-methionine and examinations with magnetic resonance (MR). The findings were related to histopathologic examination of serial stereotactic biopsies, which were guided by the appearance of the lesions on PET examination. To obtain corresponding slice orientation with the different examination techniques, an individually shaped helmet fixation was used. However, in 3 cases this fixation device could not be used for MR. Histopathologic diagnosis, obtained in all cases from multiple target stereotactic biopsies, included glioma in 9 patients and reactive gliosis in one case. A detailed comparison of the three imaging techniques and the findings at stereotactic biopsies was possible in 7 patients, while in 3 patients comparison with MR was less exact due to the patient's refusal to wear the helmet during this examination. MR was the most accurate method for outlining the total extent of a lesion, i.e. the tumor and the edema surrounding it. Four lesions had homogeneous signal characteristics and in 6 lesions two (or more) compartments could be distinguished with MR. In 5 cases the MR findings were in complete agreement with the histopathologic findings. However, a thorough correlation between signal characteristics and histology was not possible. Using PET the occurrence and the extent of tumor tissue was correctly predicted in 7 patients. The PET was normal in one case. Findings at CT were in agreement with the histopathologic diagnosis in 5 patients. MR was the most sensitive method for the detection of lesions.(ABSTRACT TRUNCATED AT 250 WORDS)     

O-(2-[18F]fluoroethyl)-L-tyrosine and L-[methyl-11C]methionine uptake in brain tumours: initial results of a comparative study

O-(2-[18F]Fluoroethyl)-L-tyrosine (FET) is a recently described amino acid analogue that has shown high accumulation in animal tumours. The aim of this study was to compare the uptake of FET with that of L-[methyl-11C]methionine (MET) in patients with suspected primary or recurrent intracerebral tumours. Sixteen consecutive patients with intracerebral lesions were studied on the same day by positron emission tomography (PET) using MET and FET. Uptake of FET and MET was quantified by standardized uptake values. Tracer kinetics for normal brain and intracerebral lesions were compared. On the basis of the MET-PET studies, viable tumour tissue was found in 13 patients. All tumours showed rapid uptake of FET and were visualized with high contrast. Mean uptake of FET for normal grey matter, white matter and tumour tissue was 1.1+/-0.2, 0.8+/-0.2 and 2.7+/-0.8 SUV, respectively. In all three tissues, uptake of MET was slightly higher (1.4+/-0.2, 0.9+/-0.1 and 3.3+/-1.0 SUV; P<0.01). However, contrast between tumour and normal tissues was not significantly different between MET and FET. Uptake of FET in non-neoplastic lesions (1.0+/-0.1 SUV) was significantly lower than in tumour tissue (P = 0.007). For all lesions there was a close correlation (r = 0.98) between MET and FET uptake. In conclusion, in PET studies of human brain tumours, the uptake and image contrast of FET appear to be very similar to those of MET. The specificity of FET for tumour tissue is promising but has to be addressed in a larger series of patients with non-neoplastic lesions.     

Role of 18F-dopa PET/CT imaging in the management of patients with 111In-pentetreotide negative GEP tumours

PURPOSE: To assess whether 18F-dopa PET/CT is able to provide information relevant in changing the clinical management of patients with gastro-enteropancreatic (GEP) tumours where there is negative or inconclusive conventional radiological imaging (ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI)) and 111In-pentetreotide scintigraphy. MATERIALS AND METHODS: From January 2005 to October 2006, 84 patients with clinical and biochemical suspicion of GEP tumours were investigated by US and CT scans, MRI and 111In-pentetreotide scintigraphy. In 13/84 (15.4%) both conventional radiological imaging and 111In-pentetreotide scintigraphy provided negative or inconclusive findings, and patients were referred for 18F-dopa PET/CT imaging. Each patient received 5.3 MBq x kg(-1) 18F-dopa intravenously, and imaged 60 min later using a hybrid PET/CT scanner. RESULTS: 18F-dopa PET/CT detected the primary tumour in all 13 patients (size range, 7-26 mm, mean, 18 mm; SUVmax range, 2.3-16.3, mean, 5.7) and further 12 unsuspected lesions (size range, 12-23 mm, mean 17; SUVmax range 2.8-12.7, mean 4.6). Confirmation of the PET/CT findings was obtained in all patients from histopathological analysis of tissue obtained after surgery and/or biopsy. All the 18F-dopa-positive primary lesions were confirmed as being the primary tumour at histology, whereas of the other 12 unsuspected 18F-dopa-positive lesions, 11 were found to be metastatic deposits and one due to unspecific inflammation (one false positive result). Notably, the results of 18F-dopa PET/CT imaging changed the clinical management in 11/13 patients (84%). CONCLUSIONS: Our preliminary results suggest that 18F-dopa PET/CT has a promising role in GEP patients with negative or inconclusive findings at conventional radiological imaging and 111In-pentetreotide scintigraphy. The findings were helpful in biopsy guidance and played a major role in changing the management of those patients.